| Radiation therapy is carefully planned. Once the proper dose of radiation has been determined, it is usually divided into several small doses administered over several weeks to give the necessary dose of radiation to the cancer, sparing as much normal tissue as possible. Both dose and time schedule vary according to the type of cancer.
Radiation therapy can be given by an external beam or by implanting radioactive material in the cancerous growth. Other methods include intraoperative radiotherapy, total body irradiation, and radiation surgery.
In external beam radiation therapy, the most common type, the radiation is aimed at the cancer from a source outside the body. The beam penetrates through the skin to reach deeper tissues. Another method uses electrons produced by a machine called a linear accelerator.
Implantation methods (brachytherapy or seeding) use radioactive material that is placed in or very close to the tumor. These sources may be described as either interstitial or intracavitary. The interstitial method places the radioactive matter directly into the tumor, for example, into the prostate gland. The intracavitary method places the sealed radioactive source in a body cavity close to the tumor, such as in the cervical canal.
If the tumor is deep within the body, radiation therapy can be given at the time of surgery (intraoperative radiotherapy), when surrounding organs can be moved out of the way. This allows a larger single dose to be delivered directly to the tumor without damaging surrounding normal tissues. Due to complexity and expense, this method is only used in special cases.
Total body irradiation is used in certain cases, such as when an individual is preparing for bone marrow transplantation. Radiation can be given in higher doses than normal because the bone marrow will be replaced.
Other radiation treatment methods include neutron and proton therapy and the use of heavy ions and pions. These treatments are used primarily in specialized radiation oncology centers. |
Source: Medical Disability Advisor